A study will be conducted to determine the therapeutic efficacy of prednisone, azathioprine, and salicylazosulfapyridine in Crohn's disease of the small intestine, and/or colon by a double-blind, randomized, controlled trial carried out by cooperating university medical centers. The effects of these drugs will be studies in patients with active and symptomatic disease, and patients whose disease is clinically quiescent. Selection of patients will be based on rigid criteria. The effect of treatment regimens on symptoms, physical findings, laboratory tests, and X-rays will be assessed serially over defined periods for up to two years.